In various types of construction sites such as construction work and civil engineering work, various types of work machines such as a bulldozer and a wheel dozer are often used. These types of work machines include a blade as a working implement. This type of blade is widely used for dozer work such as for digging soil carrying, banking, compaction and leveling.
In order to maximize working efficiency in these types of work machines, it is important for a blade to satisfy various requirements. Exampled of the requirements can be provided by increase of the amount of soil carrying per one cycle (blade capacity) as much as possible, reduction of resistance in digging and soil carrying, suitability for various types of soil for prevention of stick of the soil on a blade in digging, and the like. Also, banking, compaction, and leveling are preferably performed by one blade that satisfies above requirements. The reason is that such a blade can extremely improve working efficiency. If the structure, shape, width, height, position and digging angle of edge section (cutting edge) and the like of a blade are determined to satisfy these requirements, it is possible to provide advantages that improve the working efficiency of a work machine, reduce fuel consumption, and shorten the total construction time, for example. Also, to optimize the working performance of a bulldozer, in the power balance in the soil carrying work, it is necessary that the traction force of the bulldozer is higher than soil carrying resistance, and the driving force of the machine is higher than the traction force of the bulldozer.
The engine power that is required for digging and soil carrying work in a bulldozer is mostly consumed for the driving force of the machine, the traction force in digging and soil carrying, and the like. Accordingly, it is important to reduce the amount of energy loss in power transmission to improve fuel efficiency. Also, it is strongly required to reduce resistance in digging and soil carrying, and the like. Generally, medium-sized and small bulldozers are used for soil carrying in a short distance as compared with a large bulldozer. If the aforementioned requirements are satisfied, the engine power in digging and the soil carrying can be effectively used even in the case of a blade with the same capacity as a conventional blade or conventional traction force.
The present applicant has been already proposed a novel and unique structure of a blade in WO2004/044337A1 as one example of a blade device that increases the working amount of this type of work machine, for example.
The blade that is disclosed in WO2004/044337A1 includes a central front face section, interposition front portions that extend to be bent and inclined rearward from the right and left ends of the central front face section, and side front portions that extend to be bent and inclined frontward from the interposition front portions. In addition to this, the lower end of the central front face section has a predetermined blade width that extends in right and left directions perpendicularly to a digging direction, and a first edge section is arranged on the lower end of the central front face section. Second and third edge sections are arranged on the lower ends of the interposition front portions and the side front portions. In addition to this, an intersection line between each interposition front portion and each side front portion, and an intersection point between edges of each second edge section and each third edge sections are located rearward of the edge of the first edge section in top view. Thus, the front surface of each of the central front face section, the interposition front portions and the side front portions forms a unique shape that is defined by a curved surface that is continuously recessed from the top ends to the bottom ends.
Examples of work machines to which the blade in WO2004/044337A1 is adopted are provided by construction and earthmoving machines, for example. Typical examples of the construction and earthmoving machines are provided by a bulldozer, a wheel dozer, a motor grader, and the like. Note that “in front view”, “in top view”, and “in side view” used in the present specification refer to in front view, in top view, and in side view in the case where the blade touches the ground at an edge angle of high digging efficiency.
The aforementioned blade is similar to conventional blades from the viewpoint that the aforementioned blade includes the central front portion that composes a part of front surface of the blade, and the left and right side front portions that extend to be inclined frontward in the both, left and right sides of the blade. However, the aforementioned blade is very different from conventional blades from the viewpoint that the aforementioned blade includes the interposition front portions that are arranged between the aforementioned central front portion and the aforementioned side front portions and extend to be bent and inclined rearward from the left and right ends of the aforementioned central front portion, and the aforementioned left and right side front portions that extend to be bent and inclined frontward from the rear end edges of the interposition front portions.
A blade device is disclosed that has a relatively similar shape to a blade shape of the present invention but is used for work different from various types of work such as digging, soil carrying, and leveling in International Publication WO93/22512. The blade device disclosed in WO93/22512 is applied to a landfilling compacting machine that spreads and compacts trash in a landfill site or the like. The blade includes end blade portions, one plate of flat central blade portion, and a rectangular protruding portion. The end blade portions are arranged in left and right sides of the blade to protrude to be bent and inclined in a wing shape toward a traveling direction of the machine similar to a conventional U-shaped blade. The central blade portion is coupled between the left and right end blade portions. The protruding portion is arranged in the central part of the central blade portion and is inclined downward at the middle of the central blade in the vertical direction to protrude toward the traveling direction of the machine. In the case where the lower surface of the aforementioned protruding portion is placed along the machine traveling surface, the lower ends of the aforementioned end blade portions and central blade portion are also placed along the machine traveling surface.
Also, driving units of the aforementioned compaction machine use steel wheels, and compact trash or the like by means of these wheels. Here, a posture in that the lower ends of the aforementioned end blade portions and central blade portion in the blade device are orientated parallel to the traveling surface of the wheels is referred to as a first position, and a posture in that the blade is moved upward and inclined frontward is referred to as a second position. In the first position, the compacting machine travels to spread trash and soil in the horizontal direction. In the second position, the aforementioned protruding portion in the central part of the blade controls the amount of trash and soil that are brought into space between left and right wheels. In other words, the aforementioned protruding portion restricts the height of trash that is brought into the aforementioned space. In addition to this, in the second position, trash and soil are brought to compaction areas by the wheels through the space between the lower ends of the aforementioned side blade portions and the central blade portion, and the aforementioned traveling surface to control the amount of trash and soil.
As stated above, the blade device that is disclosed in WO93/22512 is developed mainly to provide function that spread trash and the like, and function that control the compaction amount of trash and the like, and prevent damage to the lower surface of the machine caused by an excess amount of trash that is brought into the space that is formed between the left and right wheels as compacting members by controlling the amount of trash that is brought into the aforementioned space. Accordingly, it can be understood that the blade shape of the present invention and the blade that is disclosed in this publication have the following large differences based on comparison between the blade shape and the blade that have essentially different function from each other.
That is, (1) in order that the central front portion of the blade that is disclosed in the foregoing WO2004/044337A1 can gather and hold a large amount of excavated soil, the blade have a continuous surface from the upper end to the lower end of the central part of the blade. On contrary to this, since the central protruding portion of the blade in the foregoing WO93/22512 corresponding to this central front portion mainly serves to prevent an excess amount of trash, the central protruding portion protrudes from the middle to the lower end of the central blade portion in the vertical direction. (2) In WO2004/044337A1 the intersection line between each of the pair of, left and right interposition front portions and each of the pair of, left and right side front portions is located rearward relative to the central front portion in top view, and the front ends of side front portions extend in proximity to the elongation line of the lower end of the central front portion. On contrary to this, although not described in WO93/22512, with reference to the drawings in WO93/22512, the front ends of the pair of, left and right side blade portions that protrude frontward from the central blade portion are positioned frontward relative to the protruding lower end of the central protruding portion.
As stated above, these differences result from the difference of essential function between the blade device of the invention and the blade device that is disclosed in the publication.
In the aforementioned blade that is proposed in WO2004/044337A1, the first edge section of the central front portion and the front ends of the third edge sections of the aforementioned side front portions are substantially aligned, or the third edge sections are positioned slightly rearward of the first edge section. As a result, the aforementioned first edge section excavates earth prior to the third edge sections that are arranged on the lower end of the side front portions. Accordingly, the digging power of the interposition front portions and the side front portions is reduced, and this reduction can facilitates digging. However, in actual use, the front end of the aforementioned third edge section may protrude slightly frontward of the first edge section in some cases. In such cases, the front end of the third edge section will excavate earth prior to the first edge section. But, the amount of protrusion is very small. The substantial digging power of the whole third edge section of the aforementioned side front portion is very small as compared with the digging power of the aforementioned first edge section. Such protrusion has no effect.
Accordingly, in the blade that is disclosed in the foregoing WO2004/044337A1, the traction force that acts on the aforementioned third edge section is greatly reduced as compared with conventional blades. Also, the resistance such as digging resistance and soil carrying resistance acts substantially uniformly on the aforementioned first edge section and the aforementioned third edge sections. Also, the traction force effectively acts on both the aforementioned first edge section and the aforementioned third edge section. As a result, soil that is excavated by the aforementioned third edge sections and soil that is excavated by the aforementioned first edge section are smoothly gathered through the second edge sections. Also, an intersection area that is interposed between the interposition front portion and the side front portion serves as a soil holding portion. Accordingly, it is possible to effectively hold a large amount of carried soil.
The synergistic effect by these actions can reduce the aforementioned resistance, and can greatly increase the amount of soil per traction force. In addition to this, the consumption power in digging and the soil carrying can be greatly reduced. The amount of digging and soil carrying can be maximized with a minimum energy amount in a short time. The fuel efficiency of the aforementioned work machine is remarkably improved. As a result, it is possible to reduce cost per earthwork amount.
In the most cases, in this type of blade, the front surface of a blade is formed in an arc-shaped surface that continuously extends at a predetermined curvature radius in the vertical direction and is recessed rearward.